1. Field of the Invention
This invention relates to calcined, high surface area, particulate matter. More particularly, the invention relates to such matter made by a specified calcining of clay mineral, feldspar, zeolite, coal ash, fly ash, pozzolan, volcanic ash, or mixtures thereof. Also the invention relates to treating aqueous material containing inorganic, organic, or both impurities in water solution or dispersion to remove at least some of said impurities, where the treating agent is said defined particulate matter, alone or in combination with other water treating agents.
2. Description of the Prior Art
This is an era of superconsciousness of and superconcern for the total environment surrounding the human race. Not only is there concern for degradation of the environment but also a consuming desire for a return to, as closely as technology permits, a pristine condition of nature unspoiled by human intrusion.
This desire for purity is especially strong in the field of water, resulting in efforts to get industry to return waste water to nature purer than the original raw water. Even rain water has become the subject of scrutiny, e.g., acid rain.
The treatment of sewage is an old art, with primary treatment to remove suspended particles above colloidal size; secondary treatment to remove dissolved material and/or colloidal matter; and tertiary treatment such as removal of organic materials escaping the secondary treatment. "Sludge" is produced by sewage treatment in such vast quantities that disposal has become a major headache. Landfill is most commonly used by inland communities, but landfill has its own problems, such as, odors, toxic gases released to the atmosphere, and leaching of the sludge by rain and surface water, followed by seepage of such leach water underground into ground water sources may, and often does, result in serious pollution situations with respect to potable water.
Industrial waste water presents a unique problem for each type of industry, e.g., steel mill waste water; sulfite paper pulp production; paper mill white water; petroleum refining which produces water soluble as well as water insoluble hydrocarbonaceous wastes; the acid water escaping from coal mines; etc. A difficult problem exists in the waste water from the metal plating industry and metal finishing industry because the heavy metal ions in the waste water are toxic to life and must be essentially completely removed to prevent contamination of ground water by seepage from ponds or lagoons containing such liquid waste containing complexed heavy metal ions or concentrates of such. Plastic liners are not really satisfactory answers to such seepage.
Organic polyelectrolytes are often excellent flocculating agents for dispersed material impurity, but generally such flocs have an expensively slow settling rate. A floculent with rapid settling properties is much sought after. A flocculant with chemisorption property to remove dissolved ions, especially heavy metal ions, is especially sought after.
Special compounds are being used in certain water involved industries to improve their product or the quality of the "waste water". Hydrazine is used to scavenge dissolved oxygen from boiler feed water, but hydrazine is toxic and its use severely regulated. Wood pulp bleaching, clay bleaching, and heavy metal ion waste water use borohydride, even though this expensive agent is unstable at the conditions normally existing in these aqueous media, forcing the use of a large excess of the agent; furthermore, this agent may introduce toxic boron into water supplies.
Dithionite is effective in reducing metal ions in aqueous solution to the metals, or hexavalent chromium to trivalent chromium. Acid medium interferes with the activity of the dithionite. The use of dithionite in wood pulp bleaching is impeded by the acidity of that medium. Dithionit in the moist condition is extremely unstable in storage; it can explode releasing toxic sulfur oxides. Also when dithionite contacts organic material and/or acids, a high explosive is formed which also releases toxic gases.